1. Field of the Invention
The present invention concerns a method and composition for treating skin disorders, such as rosacea and sensitive skin, with free radical scavengers, which are also known as antioxidants. More particularly, the present invention involves the treatment of rosacea by the topical application of a cosmetically acceptable formulation containing free radical scavenging compounds. The terms "radical scavenger(s)" and "antioxidant(s)" are used interchangeably herein.
Numerous cosmetic and medical treatments have been developed in an attempt to treat sensitive skin and related conditions. The condition of sensitive skin is evidenced as a tendency of the skin towards flushing and blushing. The skin disorder rosacea is an example of such a related condition. It is a common skin disorder that manifests itself, at different stages, as vivid skin redness, prominent vascularization, papules, pustules and swelling, as well as a predisposition to flushing and blushing. Rosacea is normally localized on the cheeks, chin, nose and forehead, but can also occur in the retroauricular areas, or on the chest, neck, back or scalp. Although the disorder has been observed in all age groups and in both genders, it is more common in women between the ages of 30 and 50 years. Also, it is most widespread in fair-skinned people.
The predisposition to flushing and blushing can be evoked by a variety of non-specific stimuli including UV light, heat, cold, chemical irritation, emotions, alcoholic beverages, spices, coffee and tea. In general, the rosacea-afflicted skin is abnormally sensitive to chemical and physical insults. The frequent flushing and blushing in rosacea eventually leads to permanent skin redness.
The exact mechanisms responsible for the flushing and blushing response in rosacea patients, and the cause of rosacea, are unknown. Several hypotheses have been put forward but none have taken root due to a dearth of scientific observations. It has been proposed that the causes of rosacea may be one or several of the following: (i) alimentary, (ii) psychological, (iii) pharmacological, (iv) infective, (v) climatic and (vi) immunological.
Current treatments for rosacea include the following:
(1) Antibiotics, such as topical tetracyclines, clindamycin, and erythromycin, have been used. Tetracycline is effective orally but not topically. PA1 (2) Metronidazole has been used as a topically applied gel. Metronidazole 0.75% gel is sold under the trademark MetroGel. The gel has an effect on papules and pustules, but has been reported to be ineffective against skin redness, telangiectases or flushing. PA1 (3) Drying lotions with 2% to 5% sulfur have been used to treat rosacea. Sulfur creams have obvious aesthetic disadvantages. PA1 (4) Imidazole drugs, e.g. ketoconazole, have been shown useful to treat rosacea. These drugs are potent antimicrobial agents and the safety of their continuous use by chronic rosacea patients is questionable. PA1 (5) Corticosteroid drugs are used only in severe cases. However, the potential side effects limit the duration and the skin area of corticosteroid treatment. PA1 (6) Retinoids, such as 13-cis retinoic acid, (isotretinoin), have been used for systemic treatment of rosacea but with far greater risks of side effects than, for example, antibiotics.
2. Description of the Prior Art
In addition, various patents and patent applications address the treatment of rosacea and sensitive skin.
For example, U.S. Pat. No. 5,569,651 to Garrison et al., assigned to the assignee of the present application, teaches the use of formulations containing a combination of salicylic acid and lactic acid to address sensitive skin and rosacea.
European Patent Application No. EP 756,862 A1 to L'Oreal describes the use of bradykinin antagonists to treat sensitive skin and rosacea.
In European Patent No. 737,471 A2 to L'Oreal, the applicant claims that alkaline earth metal salts are beneficial in ameliorating rosacea.
European Patent Application No. 734,729 A1 to L'Oreal claims that a calcitonin gene related peptide antagonist is useful for treating rosacea of neurogenic origin when incorporated into topical formulations.
European Patent Application No. EP 722,928 A1 to Centre International de Recherches Dermatologiques Galderma claims that certain bicyclic aromatic compounds that affect cell proliferation are useful for treating a variety of skin conditions including rosacea.
Substance P antagonists in a topical formulation are claimed in European Patent Application No. EP 722,722 A1 to L'Oreal for treating "neurogenic skin reddening."
USSR Patent Application No. SU 1776411 A1 describes a method for treating rosacea by using trichopol and additional agiotropic preparations, and ointment containing trichopol, camphor oil, solutions of adrenaline and retinol acetate.
U.S. Pat. No. 5,438,073 to Saurat et al. claims the use of dermatological compositions containing retinoids for treatment of rosacea.
German Patent Application No. DE 4123615 A1 to Albert Weinberg proposes to treat rosacea with a cosmetic tonic containing amino acids.
A topical aqueous gel containing metronidazole and polyacrylic acid for treating rosacea is described in U.S. Pat. No. 4,837,378 to Borgman. A similar system is described in PCT Patent Application No. WO 88/06888 to Curatek Pharmaceuticals, Inc.
PCT Patent Application Publication No. WO 88/00465 to Schering Aktiengesellschaft Berlin und Bergkamen teaches the use of C.sub.7 -C.sub.13 dicarboxylic acids, preferably azelaic acid, to treat rosacea.
PCT Patent Application Publication No. WO 93/20817 teaches a method of treating superficial inflammation associated with rosacea by topically applying compositions containing specific nitroimidazoles disclosed therein.
German Patent Application No. DE 3514724 A1 to Albin F. Jereb suggests that a combination of precipitated sulfur, vitamins, progesterone, testosterone propionate and menthol could lead to improvements in rosacea.
U.S. Pat. No. 4,133,893 to Spangler, describes the use for rosacea treatment of a topical formulation containing 1,1-dichloro-2-O-(-chlorophenyl)-2-(p-chlorophenyl)ethane.
Alternate treatments for rosacea and sensitive skin, that are more effective or that have fewer drawbacks, are needed.